Visual motion induces synchronous oscillations in turtle visual cortex.

Abstract

In mammalian brains, multielectrode recordings during sensory stimulation have revealed oscillations in different cortical areas that are transiently synchronous. These synchronizations have been hypothesized to support integration of sensory information or represent the operation of attentional mechanisms, but their stimulus requirements and prevalence are still unclear. Here I report an analogous synchronization in a reptilian cortex induced by moving visual stimuli. The synchronization, as measured by the coherence function, applies to spindle-like 20-Hz oscillations recorded with multiple electrodes implanted in the dorsal cortex and the dorsal ventricular ridge of the pond turtle. Additionally, widespread increases in coherence are observed in the 1-to 2-Hz band, and widespread decreases in coherence are seen in the 10-and 30-to 45-Hz bands. The 20-Hz oscillations induced by the moving bar or more natural stimuli are nonstationary and can be sustained for seconds. Early reptile studies may have interpreted similar spindles as electroencephalogram correlates of arousal; however, the absence of these spindles during arousing stimuli in the dark suggests a more specific role in visual processing. Thus, visually induced synchronous oscillations are not unique to the mammalian cortex but also occur in the visual area of the primitive three-layered cortex of reptiles.

Visual shape recognition with contour propagation

“…But one may take this a step further and suggest that contours are actually propagated in the nervous system. This may take place in the form of traveling waves, which have been observed in salamander retina (Jacobs and Werblin 1998) and in primary visual cortex of monkeys and turtles (Grinvald et al 1994;Prechtl 1994;Prechtl et al 1997Prechtl et al , 2000Bringuier et al 1997;Senseman 1999). Most of these described waves are slow (millimeters/seconds) and may suffice, for example, to explain learning processes like the establishment of the CPF (although the turtle cortex does not have orientation columns).…”

“Split Mind” and EEG Gamma Activity in Schizophrenia

“…Also Roelfsma et al (1997) in their research show that the cats waiting for a stimulus related to reward conscientiously showed strong Gamma synchrony. Also other animal studies have shown that Gamma synchrony predominantly is augmented by selective attention that augments the perception and representation of relevant stimuli (Prechtl, 1994).…”

Computing with Biologically Inspired Neural Oscillators: Application to Colour Image Segmentation

“…It has been observed in mammals, amphibians, and insects [29,41,42]. It has been measured in the monkey motor cortex [43] and across different hemispheres of the brain in the visual cortices of cats [44].…”